1. Field of the Invention
This invention relates to monitoring systems and, in particular, to an automatic television measuring system, television apparatus and method for measuring the length of a selected dimension of an object. The present invention is adapted for use with a television microscope system wherein an article having a dimension of relatively small size to be measured, in the order of 0.050 inches or smaller (depending on the resolution of the video camera), is positioned in the viewing station of the television microscope system. The television microscope system televises the article and includes in the video signals generated by the television microscope system information in the form of black/white level contrast which is representative of the dimensional measurement of the article.
The automatic measuring system of the present invention is responsive to the information contained in the video information signals and to the horizontal sweep voltage derived from normal operation of the video camera part of the television microscope system to produce an analog output voltage, direct visual readout or other graphic indicia representing a method for automatically measuring the dimensional measurement of an object is disclosed.
2. Description of the Prior Art
Television microscope measuring systems are known in the art. In one known measuring system, dimensional measurement of a pattern is achieved by televising and displaying the pattern on a television monitor and superimposing thereon a special effect or measuring raster. The superimposed measuring raster overlaps at least one dimension of the pattern to be measured. The known measuring system detects when the video signal of the pattern exceeds a fixed threshold value representative of an abrupt change of black to white level, or vice versa, representative of the end measuring point of the dimensional pattern. In addition, the known measuring system utilizes the special effect or measuring raster, which is responsive to horizontal synchronization signals, to enable a variable frequency pulse generator to generate a number of pulses representative of the elapsed time between discrete changes in black/white levels in the video signal during a horizontal scan line. A digital pulse counter is responsive to the pulse generator to accumulate, count and convert the number of pulses to a visual readout representative of the dimensional measurement of the article. Measurement is, in essence, accomplished by generating a series of pulses representative of a definitive portion of a time interval of a horizontal scan line and converting the so generated pulses into a signal or readout representative of the dimensional pattern so measured.
One disadvantage of the prior art measuring system is that a special effects raster generator having a plurality of variable period one-shot multi-vibrators is required. Further, the basic reference is the scan time between abrupt changes in black/white voltage level of the video signal, which is converted into a series of pulses and counted by a pulse counter.
The synchronization between the special effects raster generator, the one-shot multi-vibrators, the time period of the vibrators, the enabling and disabling of the variable frequency pulse generator, and the pulse counting is necessary to insure accurate measurement. Also, the synchronization of the above must, in turn, be synchronized to the synchronizing signals, blanking signals and other control signals which comprise the composite video signal.
Another known manual measuring system utilizes a television microscope in combination with a manually adjustable measuring point and ending measuring point. The adjustment is made directly in the television scan pattern. The reference or beginning measuring point is manually set by use of a television monitor to coincide with the beginning point of the dimensional measurement of the object to be measured. A second point or end point is manually set to correspond with the end of the dimensional measurement of the object. Dimensional measurement is obtained by measuring the voltage level of a horizontal sweep voltage occurring at each of the beginning and end points in the horizontal scan line. The difference in voltage levels is converted to an analog output voltage, which voltage is then converted to a visual readout representative of the distance between the two manually set reference points.
The manual measuring system has a certain disadvantage in that each measurement requires an operator to manually adjust the beginning point and ending point for each measurement. In certain applications automatic measuring of an object is desired for accuracy, consistency and rapid processing of measured objects.